The present invention relates to a multilayered polymeric body of optically thick, thin, and/or very thin plate-like or ribbon-like layers of one or more polymers within a matrix of another polymer, which body reflects light and can be fabricated to have a silvery or hued (i.e., gold, copper, etc.) metallic appearance, or a nonconventional hued (i.e., blue, green) appearance, or even an iridescent appearance, and to methods of producing such a polymeric body.
Conventional methods for fabricating reflective surfaces include forming such surfaces of highly polished metals. Because of the high costs and fabricating problems involved in using metals, more recently fabricators have used plastic surfaces which contain thin coatings of metal thereon. Thus, metal coated plastic articles are now commonly found as both decorative and functional items in a number of industries. Such articles are used as bright work for consumer appliances such as refrigerators, dishwashers, washers, dryers, radios, and the like. These types of articles are also used by the automotive industry as head lamp reflectors, bezels, radio knobs, automotive trim, and the like.
Typically, such metal coated plastic articles are formed by electroplating or by the vacuum, vapor, or chemical deposition of a thin metal layer on the surface of the article. Additionally, such coatings are subject to the chipping and flaking of the metal coatings as well as corrosion of the metal over time. If additional protective layers must be applied over the metal coating to protect it, additional labor and materials costs are involved. Further, there may be environmental disposal problems with some metal deposition processes.
One such vacuum metallized deposition system to produce bright work and automotive decorative trim is taught by Eisenfeller in U.S. Pat. Nos. 4,713,143, 4,431,711, and 4,407,871. That system deposits minute specular islands of indium metal on a dielectric substrate. The metal is then encapsulated in a clear polymer.
The preparation of multilayer articles of polymers are known, as are methods and apparatuses for making such articles. For example, such multilayered articles may be prepared utilizing multilayer coextrusion devices as described in commonly-assigned U.S. Pat. Nos. 3,773,882 and 3,884,606 to Schrenk. Such devices are capable of simultaneously extruding diverse thermoplastic polymeric materials in continuous layers having substantially uniform layer thicknesses. The number of layers may be multiplied by the use of a device as described in commonly-assigned U.S. Pat. No. 3,759,647 to Schrenk et al.
Im et al, U.S. Pat. No. 4,540,623, teaches a multilayer laminated article which includes a polycarbonate as one of the alternating continuous layers. The articles of Im, however, are intended to be transparent rather than reflective and to exhibit optical properties comparable to a pure polycarbonate polymer.
Alfrey, Jr. et al, U.S. Pat. No. 3,711,176, teaches a multilayered highly reflective thermoplastic body fabricated using thin film techniques. That is, the reflective thin film layers of Alfrey, Jr. et al relied on the constructive interference of light to produce reflected visible, ultraviolet, or infrared portions of the electromagnetic spectrum. Such reflective thin films have found use in decorative items because of the iridescent reflective qualities of the film.
The films of Alfrey, Jr. et al are extremely sensitive to thickness changes, and it is characteristic of such films to exhibit streaks and spots of nonuniform color. Further, color reflected by such films is dependent on the angle of incidence of light impinging on the film. Thus, such films are not practical for uses which require uniformity of reflectivity. Moreover, such films are not practical to thermoform into articles where uniformity of light reflectance is needed as localized thinning of the layers during thermoforming causes alterations in the reflective characteristics of the films.
Moreover, both the Alfrey, Jr. et al films and the multilayer films and articles made up of substantially continuous layers, such as those described in commonly-assigned U.S. Pat. Nos. 5,122,905 and 5,122,906, have some limiting characteristics inherent in their construction. The continuous layers must adhere to themselves to hold the film together. This may necessitate the use of intervening adhesive layers which could adversely affect the optical properties of the film and certainly add to the overall thickness of the film. Further, no gas or other fluid can be permitted at the interface between any of the layers as this may contribute to the delamination of the layers. Additionally, each of the materials used in the layers exerts an effect on the overall mechanical properties of the film. For example, if one of the polymers used is brittle, the layers of brittle material will have an effect on the overall properties of the multilayer film.
Accordingly, there remains a need in the art for a polymeric reflective film, sheet or body which can be fabricated into a variety of parts and which can exhibit a uniform reflective appearance or a silvery iridescent appearance over a range of processing conditions and part geometry. There is also a need for a polymeric reflective film or body which will hold together even if some or all of the individual layers do not, there is a need for a body in which gas or other fluid can be present at layer interfaces without adversely affecting the optical and mechanical properties of the body, and there is a need for a multilayer reflective body which has mechanical properties which are substantially independent of the mechanical properties of at least some of the layers in the body.